Merge lp:~akopytov/percona-server/tp-high-prio-mode-5.5 into lp:percona-server/5.5

[Alexey Kopytov]

    Implementation of
    https://blueprints.launchpad.net/percona-server/+spec/tp-high-prio-mode-5.5

    Introduced a new Thread Pool option, thread_pool_high_prio_mode, which
    accepts the following values:

    - “transactions” (the default). In this mode only statements from
      already started transactions may go into the high priority queue
      depending on the number of high priority tickets currently available
      in a connection (see thread_pool_high_prio_tickets);

    - “statements”. In this mode all individual statements go into the high
      priority queue, regardless of connection’s transactional state and the
      number of available high priority tickets. This value can be used to
      prioritize AUTOCOMMIT transactions or other kinds of statements such
      as administrative ones for specific connections. Note that setting
      this value globally essentially disables high priority scheduling,
      since in this case all statements from all connections will use a
      single queue
      (the high priority one);

    - “none”. This mode disables high priority queue for a connection. Some
      connections (e.g. monitoring) may be insensitive to execution latency
      and/or never allocate any server resources that would otherwise impact
      performance in other connections and thus, do not really require high
      priority scheduling. Note that setting thread_pool_high_prio_mode to
      “none” globally has essentially the same effect as setting it to
      “statements” globally: all connections will always use a single queue
      (the low priority one in this case).

http://jenkins.percona.com/view/PS%205.5/job/percona-server-5.5-param/908/

[George Ormond Lorch III (gl-az)]

review: Approve (g2)

[Alexey Kopytov (akopytov)]

Spotted an inconsistency in naming (threadpool_high_prio_tickets vs. thread_pool_high_prio_mode). Will fix in a separate revision and push.

review: Needs Fixing

[Alexey Kopytov (akopytov)]

review: Approve

=== modified file 'Percona-Server/mysql-test/r/percona_server_variables_debug.result'
--- Percona-Server/mysql-test/r/percona_server_variables_debug.result	2013-09-24 12:47:59 +0000
+++ Percona-Server/mysql-test/r/percona_server_variables_debug.result	2013-12-12 13:56:05 +0000
@@ -385,6 +385,7 @@
 THREAD_CACHE_SIZE
 THREAD_CONCURRENCY
 THREAD_HANDLING
+THREAD_POOL_HIGH_PRIO_MODE
 THREAD_POOL_HIGH_PRIO_TICKETS
 THREAD_POOL_IDLE_TIMEOUT
 THREAD_POOL_MAX_THREADS

=== modified file 'Percona-Server/mysql-test/r/percona_server_variables_release.result'
--- Percona-Server/mysql-test/r/percona_server_variables_release.result	2013-08-28 21:14:46 +0000
+++ Percona-Server/mysql-test/r/percona_server_variables_release.result	2013-12-12 13:56:05 +0000
@@ -373,6 +373,7 @@
 THREAD_CACHE_SIZE
 THREAD_CONCURRENCY
 THREAD_HANDLING
+THREAD_POOL_HIGH_PRIO_MODE
 THREAD_POOL_HIGH_PRIO_TICKETS
 THREAD_POOL_IDLE_TIMEOUT
 THREAD_POOL_MAX_THREADS

=== added file 'Percona-Server/mysql-test/suite/sys_vars/r/thread_pool_high_prio_mode_basic.result'
--- Percona-Server/mysql-test/suite/sys_vars/r/thread_pool_high_prio_mode_basic.result	1970-01-01 00:00:00 +0000
+++ Percona-Server/mysql-test/suite/sys_vars/r/thread_pool_high_prio_mode_basic.result	2013-12-12 13:56:05 +0000
@@ -0,0 +1,34 @@
+SET @start_global_value = @@GLOBAL.thread_pool_high_prio_mode;
+SET @@GLOBAL.thread_pool_high_prio_mode=DEFAULT;
+SELECT @@GLOBAL.thread_pool_high_prio_mode;
+@@GLOBAL.thread_pool_high_prio_mode
+transactions
+SET @@SESSION.thread_pool_high_prio_mode=DEFAULT;
+SELECT @@SESSION.thread_pool_high_prio_mode;
+@@SESSION.thread_pool_high_prio_mode
+transactions
+SHOW GLOBAL VARIABLES LIKE 'thread_pool_high_prio_mode';
+Variable_name	Value
+thread_pool_high_prio_mode	transactions
+SHOW SESSION VARIABLES LIKE 'thread_pool_high_prio_mode';
+Variable_name	Value
+thread_pool_high_prio_mode	transactions
+SET @@thread_pool_high_prio_mode='transactions';
+SELECT @@thread_pool_high_prio_mode;
+@@thread_pool_high_prio_mode
+transactions
+SET @@thread_pool_high_prio_mode='statements';
+SELECT @@thread_pool_high_prio_mode;
+@@thread_pool_high_prio_mode
+statements
+SET @@thread_pool_high_prio_mode='none';
+SELECT @@thread_pool_high_prio_mode;
+@@thread_pool_high_prio_mode
+none
+SET @@thread_pool_high_prio_mode='foo';
+ERROR 42000: Variable 'thread_pool_high_prio_mode' can't be set to the value of 'foo'
+SET @@thread_pool_high_prio_mode=1.1;
+ERROR 42000: Incorrect argument type to variable 'thread_pool_high_prio_mode'
+SET @@thread_pool_high_prio_mode=1e1;
+ERROR 42000: Incorrect argument type to variable 'thread_pool_high_prio_mode'
+SET @@GLOBAL.thread_pool_high_prio_mode = @start_global_value;

=== added file 'Percona-Server/mysql-test/suite/sys_vars/t/thread_pool_high_prio_mode_basic.test'
--- Percona-Server/mysql-test/suite/sys_vars/t/thread_pool_high_prio_mode_basic.test	1970-01-01 00:00:00 +0000
+++ Percona-Server/mysql-test/suite/sys_vars/t/thread_pool_high_prio_mode_basic.test	2013-12-12 13:56:05 +0000
@@ -0,0 +1,35 @@
+--source include/not_windows.inc
+--source include/not_embedded.inc
+
+SET @start_global_value = @@GLOBAL.thread_pool_high_prio_mode;
+
+# Test the default value
+SET @@GLOBAL.thread_pool_high_prio_mode=DEFAULT;
+SELECT @@GLOBAL.thread_pool_high_prio_mode;
+
+# Test that the session value is accepted
+SET @@SESSION.thread_pool_high_prio_mode=DEFAULT;
+SELECT @@SESSION.thread_pool_high_prio_mode;
+
+SHOW GLOBAL VARIABLES LIKE 'thread_pool_high_prio_mode';
+SHOW SESSION VARIABLES LIKE 'thread_pool_high_prio_mode';
+
+SET @@thread_pool_high_prio_mode='transactions';
+SELECT @@thread_pool_high_prio_mode;
+
+SET @@thread_pool_high_prio_mode='statements';
+SELECT @@thread_pool_high_prio_mode;
+
+SET @@thread_pool_high_prio_mode='none';
+SELECT @@thread_pool_high_prio_mode;
+
+--error ER_WRONG_VALUE_FOR_VAR
+SET @@thread_pool_high_prio_mode='foo';
+
+--error ER_WRONG_TYPE_FOR_VAR
+SET @@thread_pool_high_prio_mode=1.1;
+
+--error ER_WRONG_TYPE_FOR_VAR
+SET @@thread_pool_high_prio_mode=1e1;
+
+SET @@GLOBAL.thread_pool_high_prio_mode = @start_global_value;

=== modified file 'Percona-Server/sql/sql_class.h'
--- Percona-Server/sql/sql_class.h	2013-12-03 05:52:35 +0000
+++ Percona-Server/sql/sql_class.h	2013-12-12 13:56:05 +0000
@@ -562,7 +562,8 @@
   my_bool expand_fast_index_creation;
   my_bool pseudo_slave_mode;
 
-  uint threadpool_high_prio_tickets;
+  uint  threadpool_high_prio_tickets;
+  ulong thread_pool_high_prio_mode;
 } SV;
 
 

=== modified file 'Percona-Server/sql/sys_vars.cc'
--- Percona-Server/sql/sys_vars.cc	2013-12-03 05:52:35 +0000
+++ Percona-Server/sql/sys_vars.cc	2013-12-12 13:56:05 +0000
@@ -2388,6 +2388,21 @@
   SESSION_VAR(threadpool_high_prio_tickets), CMD_LINE(REQUIRED_ARG),
   VALID_RANGE(0, UINT_MAX), DEFAULT(UINT_MAX), BLOCK_SIZE(1)
 );
+
+static Sys_var_enum Sys_threadpool_high_prio_mode(
+  "thread_pool_high_prio_mode",
+  "High priority queue mode: one of 'transactions', 'statements' or 'none'. "
+  "In the 'transactions' mode the thread pool uses both high- and low-priority "
+  "queues depending on whether an event is generated by an already started "
+  "transaction and whether it has any high priority tickets (see "
+  "thread_pool_high_prio_tickets). In the 'statements' mode all events (i.e. "
+  "individual statements) always go to the high priority queue, regardless of "
+  "the current transaction state and high priority tickets. "
+  "'none' is the opposite of 'statements', i.e. disables the high priority queue "
+  "completely.",
+  SESSION_VAR(thread_pool_high_prio_mode), CMD_LINE(REQUIRED_ARG),
+  thread_pool_high_prio_mode_names, DEFAULT(TP_HIGH_PRIO_MODE_TRANSACTIONS));
+
 #endif /* !WIN32 */
 static Sys_var_uint Sys_threadpool_max_threads(
   "thread_pool_max_threads",

=== modified file 'Percona-Server/sql/threadpool.h'
--- Percona-Server/sql/threadpool.h	2013-12-02 12:17:20 +0000
+++ Percona-Server/sql/threadpool.h	2013-12-12 13:56:05 +0000
@@ -15,6 +15,12 @@
 
 #define MAX_THREAD_GROUPS 128
 
+enum tp_high_prio_mode_t {
+  TP_HIGH_PRIO_MODE_TRANSACTIONS,
+  TP_HIGH_PRIO_MODE_STATEMENTS,
+  TP_HIGH_PRIO_MODE_NONE
+};
+
 /* Threadpool parameters */
 extern uint threadpool_min_threads;  /* Minimum threads in pool */
 extern uint threadpool_idle_timeout; /* Shutdown idle worker threads  after this timeout */
@@ -23,6 +29,9 @@
 extern uint threadpool_max_threads;  /* Maximum threads in pool */
 extern uint threadpool_oversubscribe;  /* Maximum active threads in group */
 
+/* Possible values for thread_pool_high_prio_mode */
+extern const char *thread_pool_high_prio_mode_names[];
+
 /* Common thread pool routines, suitable for different implementations */
 extern void threadpool_remove_connection(THD *thd);
 extern int  threadpool_process_request(THD *thd);

=== modified file 'Percona-Server/sql/threadpool_unix.cc'
--- Percona-Server/sql/threadpool_unix.cc	2013-12-12 13:56:05 +0000
+++ Percona-Server/sql/threadpool_unix.cc	2013-12-12 13:56:05 +0000
@@ -47,6 +47,10 @@
 for stall detection to kick in */
 #define THREADPOOL_CREATE_THREADS_ON_WAIT
 
+/* Possible values for thread_pool_high_prio_mode */
+const char *thread_pool_high_prio_mode_names[]= {"transactions", "statements",
+                                                 "none", NullS};
+
 /** Indicates that threadpool was initialized*/
 static bool threadpool_started= false; 
 
@@ -427,6 +431,21 @@
           > 1 + (int) threadpool_oversubscribe);
 }
 
+/*
+   Checks if a given connection is eligible to enter the high priority queue
+   based on its current thread_pool_high_prio_mode value, available high
+   priority tickets and transactional state.
+*/
+
+inline bool connection_is_high_prio(connection_t *c)
+{
+  const ulong mode= c->thd->variables.thread_pool_high_prio_mode;
+
+  return (mode == TP_HIGH_PRIO_MODE_STATEMENTS) ||
+    (mode == TP_HIGH_PRIO_MODE_TRANSACTIONS &&
+     c->tickets > 0 && thd_is_transaction_active(c->thd));
+}
+
 } // namespace
 
 /* Dequeue element from a workqueue */
@@ -758,7 +777,7 @@
     for(int i=(listener_picks_event)?1:0; i < cnt ; i++)
     {
       connection_t *c= (connection_t *)native_event_get_userdata(&ev[i]);
-      if (c->tickets > 0 && thd_is_transaction_active(c->thd))
+      if (connection_is_high_prio(c))
       {
         c->tickets--;
         thread_group->high_prio_queue.push_back(c);
@@ -1150,8 +1169,7 @@
           must either have a high priority ticket, or there must be not too many
           busy threads (as if it was coming from a low priority queue).
         */
-        if (connection->tickets > 0 &&
-            thd_is_transaction_active(connection->thd))
+        if (connection_is_high_prio(connection))
           connection->tickets--;
         else if (too_many_busy_threads(thread_group))
         {